Quality of city rivers falls short
Christchurch’s waterways are failing to meet quality standards and urban pollution is to blame, scientists say.
The Heathcote River is of most concern, with one small tributary stream having the unhealthiest water in the city, monitoring of five river catchments in 2017 found.
Twenty per cent of the samples failed overall monitoring standards, while 98 per cent of the tested sites failed at least one water health guideline.
The results were consistent with previous years. Most waterways were regarded as being in poor or fair condition.
The contaminants of most concern were nitrogen, phosphorus and E coli, as well as dissolved copper and zinc.
Two thirds of sites failed to meet E coli guidelines. In June, scientists revealed samples of the bacteria resistant to antibiotics had been found in the Avon River at Hagley Park.
Despite this, the Avon and Styx rivers saw significant improvements in water quality over time, though the Avon’s quality declined between 2016 and 2017.
The Heathcote is of greatest concern. The Christchurch City Council water quality survey found, of the 42 sites monitored across the area, the 11 worst were all in the Heathcote’s catchment.
Despite being targeted for cleaning up two years ago, two small streams that flow into the Heathcote continue to have a major impact on its health. The streams, at Haytons and Curletts roads, flow from the industrialised areas of Wigram, where stormwater is pumped directly into them.
That water is loaded with heavy metals such as copper and zinc, and high levels of ammonia and dissolved phosphorous, helping make them the worst spots in the city.
An investigationinto poor water quality at Haytons stream four years ago found its quality was not improving. It was suggested businesses in the area were failing to improve management practices.
The council and Environment Canterbury (ECan) are working with landowners to reduce contaminants getting into stormwater systems and waterways. The council has promised to upgrade stormwater treatment facilities at both Haytons and Curletts streams.
There have been improvements elsewhere, and council scientists say the water quality in most waterways is unchanged on recent years.
More than 13,000 tests were carried out at 42 sites last year for the water report, 7335 of which were assessed against guideline levels to determine water quality.
Samples were taken from the catchments of five rivers, the Avon, Heathcote, Styx, Halswell and O¯ tu¯ kaikino, a tributary of the Waimakariri.
The Avon and Styx river catchments have seen marked improvements, while the healthiest water was found at Groynes Inlet on the O¯ tu¯ kaikino River and at the Waimairi Stream in Fendalton.
The report recommends efforts to reduce contamination of Haytons and Curletts streams remain a priority.
It also calls for investigation into four other sources of particularly unhealthy water, including the Omaka Scout Camp at O¯ tu¯ kaikino Creek, particularly for E.coli and nutrient levels, which rose by almost 50 per cent last year.
A catchment plan for the O¯ tu¯ kaikino River should also be developed to maintain good water quality, the report urges.
And there should be investigations into how best to reduce contamination of waterways from animal faeces.
Christchurch is criss-crossed with waterways because it was built on a swamp. Urban waterways typically face difficulties in achieving good water quality because of the impacts of human activity.
Council waterways ecologist Dr Belinda Margetts, who led the research, said: ‘‘Most Christchurch waterways have fair or poor water quality, indicating they are historically and currently subjected to contamination, from stormwater, waterfowl and other factors.
‘‘That doesn’t mean we shouldn’t strive to have the best possible. If we could bring all our waterways up at least into the good category that would be great. I think that’s an achievable goal to work towards.’’